Rotary displacement machine having at least two annular displacement gears and supply channels

ABSTRACT

A rotary displacement machine has a housing and at least two annular displacement gears arranged in the housing and supported rotatably on a stationary axle, receptively. The at least two annular displacement gears have external teeth for conveying a fluid. At least two supply channels are provided in the housing and have a supply mouth, respectively, opening toward the annular displacement gears for supplying a fluid to the annular displacement gears. The supply mouth is configured such that, upon operation of the rotary, displacement machine, a fluid exiting from the supply mouth reaches either only the teeth of a single one of the annular displacement gears or only the teeth of the annular displacement gears rotating in the same direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a rotary displacement machine with at least twodisplacement gear wheels with external teeth for conveying a fluid andwith at least two supply channel with supply mouths in the area of thedisplacement gear wheels for supplying the fluid to the displacementgear wheels, wherein each one of the supply mouths is configured suchthat upon proper operation of the rotary displacement machine fluidexiting from the supply mouth can reach either only the teeth of asingle displacement gear wheel or only the teeth of such displacementgear wheels which rotate in the same direction. The inventionfurthermore relates to a housing for such a machine.

2. Description of the Related Art

Rotary displacement machines of the aforementioned kind can be used aspumps, i.e., as pressure generators, as well as motors, i.e. pressureconsumers. When the rotary displacement machine is used as a motor, theconveyed fluid is generally a hydraulic oil. When the machine is used asa pump, different fluids can be conveyed, particularly, however, liquidssuch as oil, water and the like.

A rotary displacement machine with the aforementioned features is knownfrom GB 2 161 861. A similar machine is also disclosed in FR 946 868.

In addition, from different documents, for example, DE 190 361 or DE 254645, rotary displacement machines are known in which displacement gearwheels with external teeth or with means comparable to such displacementgear wheels (DE 190 361) are provided wherein, however, the suppliedfluid does not reach either only the teeth of a single displacement gearwheel or only the teeth of such displacement gear wheels which rotate inthe same direction.

Other rotary displacement machines are known, for example, from DE 19533 215 A1 or DE 254 645 C1, in the form of gear pumps with twodisplacement gear wheels arranged in a housing, wherein one of thedisplacement gear wheels is driven by a drive gear wheel arranged in thehousing.

From DE 196 38 332 A1 and DE 328 963 C1, gear pumps also having twodisplacement gear wheels arranged in a housing are known in which one ofthe displacement gear wheels is driven by a shaft extending from thehousing.

Even though the known rotary displacement machines have beensuccessfully used in practice for decades, at high rotary speedsproblems result in regard to turbulences and cavitation which limit theefficiency and the applications of the machines and which have theeffect that filling of the conveying chambers formed between the teethof the displacement gear wheels is not optimal.

One basic problem are the displacement gear wheels provided in all ofthe aforementioned known rotary displacement machines because they mustbe supported in a complex way which also entails sealing problems.

SUMMARY OF THE INVENTION

Based on this, it is an object of the invention to provide a rotarydisplacement machine exhibiting easy running properties and being easilysealed and having a minimal weight. Moreover, turbulences in the supplyarea, i.e., in that area in which the medium to be conveyed istransferred from the supply channels into the conveying chambers, are tobe substantially prevented and filling of the conveying chambers is tobe improved.

The object is solved by a rotary displacement machine of theaforementioned kind in which the displacement gear wheels ere configuredin the form of annular displacement gears rotatably supported about astationary axle, respectively.

Instead of classical gear wheels, annular gears are used which aresometimes also referred to as gear rings, for conveying the fluid. Inthe following, these annular gears are therefore referred to as annulardisplacement gears.

By employing annular displacement gears sealing and bearing problems canbe prevented and material can be saved so that also the weight can bereduced. Surprisingly, it was found that the rotary displacement machineembodied in this way also runs more quietly and more smoothly than theprior art rotary displacement machines of a comparable size. The annulargears can be supported in an especially simple way, and the shafts whichare required for gear wheels are no longer necessary. Depending on thesize and configuration of the annular gears, one bearing for eachannular gear can be sufficient, while rotating shafts must be supportedalways on both ends.

In a rotary displacement machine embodied in this way, well-definedfluid flows result during operation while in the case of some of therotary displacement machines known from the aforementioned prior artreferences, which have a right-handed displacement gear wheel and aleft-handed displacement gear wheel, the fluid, after exiting the supplymouth, can be entrained by the right-handed as well as the left-handeddisplacement gear wheel so that disturbing vortices and cavitations aregenerated in the fluid flow. With the embodiment according to theinvention, filling losses are reduced and the fluid can be supplied tothe displacement gear wheels such that the impulse transmitted by theflowing fluid onto the displacement gear wheels does not unnecessarilybrake the rotation of the displacement gear wheels.

Generally, a displacement machine embodied according to the presentinvention will have two meshing displacement gear wheels wherein eachone of the displacement gear wheels has at least one supply mouthcorrelated therewith. However, it is also possible to provide, forexample, four displacement gear wheels of which two are arranged on acommon axis atop one another, respectively. In the case of such amachine, it can be sufficient to provide also only two supply mouthswhen these are configured such that the exiting fluid can reach only thedisplacement gear wheels arranged on the common axis.

A principal idea in regard to the rotary displacement machine is thecorresponding guiding of the fluid flows whereby a significantimprovement of the efficiency of the rotary displacement machine can beachieved.

In a constructively especially simple configuration of a rotarydisplacement machine, only one supply channel with a number of supplymouths is provided which number corresponds to the number ofdisplacement gear wheels. Such a rotary displacement machine can bearranged in a housing of a simple configuration which must have only oneinlet for introducing the fluid into the supply channel.

For certain applications it may however also be advantageous whenseveral supply channels are provided; in particular, preferably as manyas displacement gear wheels are provided. Each supply channel can thenbe provided with its own inlet so that such a machine, when it is usedas a motor, can be operated with fluid coming simultaneously fromdifferent pressure sources and, when it is used as a pump, can suck influid from different reservoirs. The rotary displacement machine canthen advantageously also be used as a mixer.

In a preferred embodiment, the displacement gear wheels are arranged ina housing in which the supply mouths and/or the supply channel/channelsare formed by a corresponding shaping. It is then no longer necessary toprovide special components and/or seals for forming the supply mouthsand the supply channels.

In order to further improve the efficiency of a rotary displacementmachine, in which two displacement gear wheels are arranged in a housingand mesh with one another in one area (meshing area), according to anadvantageous embodiment of the invention at least one connecting channelis provided which connects directly or indirectly the meshing area withat least one conveying chamber formed between the teeth of adisplacement gear wheel and the inner side of the housing.

Such a connecting channel enables the transfer of fluid from the meshingarea into at least one conveying chamber formed between the teeth of adisplacement gear wheel so that filling of the chamber is furtherincreased. In the case of the previously known displacement pumps,connecting channels are partially also provided in the meshing area;however, they are connected with the respective reservoir from whichfluid is taken so that in the previously known machines the pressuregenerated in the meshing area is used to convey the fluid to the areawhere it should actually be sucked away.

The connecting channel/channels can be connected by corresponding linesor directly with one or several conveying chambers. It is particularlyadvantageous to form the connecting channel/channels by a correspondingshaping of the housing, in particular, in that on the inner side of thehousing surrounding the displacement gear wheels one or several groovesare provided.

The driving action (when the rotary displacement machine is used as apump) or the output action (when the rotary displacement machine is usedas a motor) can be realized advantageously in different ways adjustedoptimally with regard to the respective application. Accordingly, it ispossible to configure the machines such that at least one of thedisplacement gear wheels comprises a drive shaft or an output shaftwhich is then extended to the outer side of the corresponding housingsurrounding the displacement gear wheels where, as is known in the art,it is driven or drives, but it is also possible to provide a drive gearwheel meshing with one of the displacement gear wheels (of course, thedrive gear wheel, in the case of use of the rotary displacement machineas a motor, should be referred to as an output gear wheel but will bereferred to always as a drive gear wheel in the following for reasons ofclarity).

When such a drive gear wheel is provided, it has been found to beparticularly advantageous to arrange it in an area between thedisplacement gear wheels that is not accessible to the fluid to beconveyed.

In a preferred configuration of a rotary displacement machine with sucha drive gear wheel, the transmission ratio between the drive gear wheeland the driven (output) displacement gear wheel is greater than 1:3 andis particularly between 1:4.5 and 1:6.5. This not only reduces thetorque to be provided in the case of application as a pump; it was alsofound that such a transmission ratio also contributes advantageously toa reduction of the operating noise.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention result from the purelyexemplary and non-limiting description of a few embodiments of theinvention in connection with the drawing, in which

FIG. 1 shows a schematic cross-section of a rotary displacement machineaccording to the invention with two displacement gear wheels and a drivegear wheel;

FIG. 2 shows a schematic illustration of a part of a housing accordingto the invention for a rotary displacement machine with two displacementgear wheels;

FIG. 3 shows a schematic cross-section of a rotary displacement machinewith two meshing displacement gear wheels and with two connectingchannels connecting the meshing area with a conveying chamber,respectively; and

FIG. 4 shows schematically an embodiment with four displacement gearwheels, wherein two gear wheels are arranged on a common axis and rotatein the same direction, respectively.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a rotary displacement machine, identified in its entirety at10, is shown in which two displacement gear wheels configured as annulardisplacement gears 12 and 14 are arranged in a housing 16 such that theymesh within one area.

The annular displacement gears are supported to be rotatable about astationary axle 18 or 20, respectively. The supporting action betweenaxle and annular gear is realized by balls 22 and 24, respectively,wherein, for reasons of clarity, only a few balls are illustrated ofwhich only one is identified by reference numeral, respectively.

As indicated by the arrows 26 and 28, upon proper operation of therotary displacement machine 10 the annular displacement gear 12 to theleft in the Figure rotates right-handed while the annular displacementgear 14 to the right in the Figure rotates left-handed.

For providing a driving action or output action of the annulardisplacement gears, a drive gear wheel 30 is provided in this embodimentwhich meshes with the annular displacement gear 12 and has a diameterwhich is approximately six times smaller than that of the annulardisplacement gear 12.

The drive gear wheel 30 is arranged such in the housing 16 between theannular displacement gears 12 and 14 that it is encapsulated relative tothe incoming fluid.

For supplying fluid, two separate supply channels 32 and 34 are providedin this embodiment wherein the supply channel 32 is correlated with theannular displacement gear 12 and the supply channel 34 is correlatedwith the annular displacement gear 14, each forming only one supplymouth. At the outer side of the housing 16 connectors for supplyingfluid into the supply channels 32 and 34 are provided which are of aknown design and therefore not illustrated. An outlet 36 is provided forremoving the conveyed fluid.

During operation of the rotary displacement machine, the fluid to beconveyed flows via the supply mouths of tile supply channels 32 and 34into the conveying chambers formed between the teeth of the annulardisplacement gears 12 and 14 and is then expelled via the outlet 36, inthis embodiment after approximately three-fourths of a revolution of therespective annular displacement gear. Possibly unexpelled residualamounts of the conveyed fluid, which, depending on the configuration ofthe machine, can still be present between the teeth of the annulardisplacement gear 12 after passing the area in which the annulardisplacement gears mesh with one another, can reach the drive gear wheel30 and advantageously contribute to lubrication of the meshing area ofthe annular displacement gear 12 and the drive gear wheel 30.

In FIG. 2, a section of the housing 40 for a rotary displacement machineis shown in which two supply channels for supplying fluid to be conveyedare formed, as illustrated by dashed lines 42 and 44.

The supply channels in this embodiment have a common inlet 46, but openinto separate areas 48 and 50 of the housing which serve for receiving adisplacement gear wheel or annular displacement gear, respectively.Moreover, an outlet 52 for discharging the conveyed fluid is provided inthe housing.

FIG. 3 shows a schematic cross-section of a rotary displacement machine,referenced in its entirety at 60, with two meshing displacement gearwheels 62 and 64. The displacement gear wheels are arranged in a housing66 in which two supply channels 70 and 72 are formed which are connectedto a common inlet 68; the supply channel 70 opens at the displacementgear wheel 62 and the supply 7 channel 72 opens at the gear wheel 64.Moreover, the housing has an outlet 74.

The special inventive feature of this embodiment is illustrated by thedotted arrows 76, 78, 80, and 82 which illustrate the fluid flow enabledby the connecting channels from the meshing area, in which thedisplacement gear wheels 62 and 64 mesh with one another, to an area,respectively, across which the conveying chambers formed between theinner wall of the housing and the teeth of each displacement gear wheelpass. The fluid enclosed upon meshing of the displacement gear wheels isthus pressed advantageously into the conveying chambers and increasesfilling of the chambers and accordingly the conveying efficiency. Theconnecting channels can be realized in a cost-efficient way, forexample, by grooves G, indicated by dashed lines extending parallel tothe arrows, on the inner side 66 a of the housing 66 facing thedisplacement gear wheels. FIG. 4 shows schematically an embodiment withfour displacement gear wheels 12 a, 12 b, 14 a, 14 b of which two arearranged on a common axis 18′ and 20′, respectively, and rotate in thesame direction (arrows 26′, 28′). As mentioned before, it can besufficient to provide only two supply mouths configured such that theexiting fluid can reach only the displacement gear wheels arranged onthe common axis and rotating in the same direction.

We claim:
 1. A rotary displacement machine comprising: a housing; two ormore intermeshing annular displacement gears arranged in the housing andsupported rotatably on a stationary axle, respectively; wherein theannular displacement gears have external teeth for conveying a fluid;two or more supply channels provided in the housing and having a supplymouth, respectively, opening toward the annular displacement gears forsupplying a fluid to the annular displacement gears; wherein the supplymouth is configured such that, upon operation of the rotary displacementmachine, a fluid exiting from the supply mouth reaches either only theteeth of only one of the annular displacement gears or only the teeth ofthe annular displacement gears arranged on a common one of thestationary axles and rotating in the same direction; and a drive gearwheel meshing in operation of the rotary displacement machine with oneof the annular displacement gears, wherein the transmission ratiobetween drive gear wheel and said one annular displacement gear drivenby the drive gear is greater than 1:3.
 2. The rotary displacementmachine according to claim 1, wherein each one of the supply channelsopening in the area of one of the annular displacement gears is embodiedsuch that a flow of fluid, resulting during operation of the rotarydisplacement machine and flowing through the supply channel in thedirection toward said one annular displacement gear, is directed in atransition area between the supply channel and said one annulardisplacement gear onto flanks of the external teeth of said one annulardisplacement gear located in the transition area, wherein the flanksface in a direction opposite to the rotational direction of said oneannular displacement gear.
 3. The rotary displacement machine accordingto claim 1, wherein the transmission ratio is between 1:4.5 and 1:6.5.4. The rotary displacement machine according to claim 1, wherein thedrive gear wheel is arranged in an area located between the annulardisplacement gears, wherein the area is sealed against inflowing fluidto be conveyed.
 5. The rotary displacement machine according to claim 1,wherein the two annular displacement gears mesh with one another in ameshing area, further comprising at least one connecting channelconfigured to directly or indirectly connect the meshing area with atleast one conveying chamber formed between the external teeth of one ofthe annular displacement gears and an inner side of the housing.
 6. Therotary displacement machine according to claim 5, wherein the connectingchannel is formed by a shaping of the housing.
 7. The rotarydisplacement machine according to claim 6, wherein the connectingchannel is a groove provided on the inner side of the housing whichinner side surrounds the annular displacement gears.